ade7880 Analog Devices, Inc., ade7880 Datasheet - Page 25

• Manufacturer Part Number: ade7880
• Description: Polyphase Multifunction Energy Metering Ic With Harmonic Monitoring
• Manufacturer: Analog Devices, Inc.

Preliminary Technical Data
Current Waveform Gain Registers
There is a multiplier in the signal path of each phase and
neutral current. The current waveform can be changed by
±100% by writing a corresponding twos complement number to
the 24-bit signed current waveform gain registers (AIGAIN,
BIGAIN, CIGAIN, and NIGAIN). For example, if 0x400000 is
written to those registers, the ADC output is scaled up by 50%.
To scale the input by −50%, write 0xC00000 to the registers.
Equation 3 describes mathematically the function of the current
waveform gain registers.
Changing the content of the AIGAIN, BIGAIN, CIGAIN, or
INGAIN registers affects all calculations based on its current;
that is, it affects the corresponding phase active/reactive/
+0.5V/GAIN
-0.5V/GAIN
Current Waveform =
ADC
V
IN
0V
IAP
IAN
V
IN
V
Output
ANALOG INPUT RANGE
IN
INN
INP
x1, x2, x4,x8,
PGA1
PGA1 bits
GAIN[2:0]
x16
×
PGA2
x1, x2, x4,x8,

 

PGA2 bits
GAIN[5:3]
1
+
x16
Content
REFERENCE
of
ADC
Current
0xAEB86F=
0x514791=
-5,326,737
5,326,737
2
23
REFERENCE
0V
Gain
AIGAIN[23:0]
ADC
DSP
ADC OUTPUT RANGE
Register
CURRENT CHANNEL
DATA RANGE
Figure 16. Current Channel Signal Path
Figure 17. Neutral Current Signal Path
CONFIG3[0]
HPFEN bit
DSP
HPF
NIGAIN[23:0]

 

Rev. PrE | Page 25 of 103
(3)
INTEGRATOR
CONFIG[0]
INTEN bit
DIGITAL
CONFIG3[0]
HPFEN bit
apparent energy and current rms calculation. In addition,
waveform samples scale accordingly.
Note that the serial ports of the ADE7880 work on 32-, 16-, or
8-bit words, and the DSP works on 28 bits. The 24-bit AIGAIN,
BIGAIN, CIGAIN, and NIGAIN registers are accessed as 32-bit
registers with the four most significant bits (MSBs) padded with
0s and sign extended to 28 bits. See Figure 18 for details.
Current Channel HPF
The ADC outputs can contain a dc offset. This offset can create
errors in power and rms calculations. High-pass filters (HPFs)
are placed in the signal path of the phase and neutral currents
and of the phase voltages. If enabled, the HPF eliminates any dc
HPF
0xAEB86F=
0x514791=
-5,326,737
5,326,737
31
0V
ACTIVE AND REACTIVE
LPF1
TOTAL/FUNDAMENTAL
POWER CALCULATION
CURRENT RMS (IRMS)
CURRENT PEAK,
Figure 18. 24-Bit xIGAIN Transmitted as 32-Bit Words
OVERCURRENT
SAMPLE REGISTER
0000
IAWV WAVEFORM
INTEGRATOR
CALCULATION
DATA RANGE AFTER
CURRENT CHANNEL
DETECT
CONFIG3[3]
ININTEN bit
DIGITAL
INTEGRATOR
28 27
EQUAL TO BIT 23
BITS[27:24] ARE
ZX DETECTION
24 23
BIT 23 IS A SIGN BIT
0xAEB86F=
0x514791=
-5,326,737
5,326,737
CURRENT RMS (IRMS)
SAMPLE REGISTER
24-BIT NUMBER
INWV WAVEFORM
CALCULATION
0V
ZX SIGNAL
DATA RANGE
ADE7880
0